The regenerative capacity of Schwann cells in the PNS underlies functional repair after injury. In this study, Mindos et al. show a new function for the tumor suppressor Merlin and Hippo/YAP signaling in the generation of repair-competent Schwann cells after injury.

A minority of meningiomas are difficult to treat with surgery or radiotherapy, and chemotherapeutic alternatives are limited. This study aims to better understand pathways that are active in meningiomas, in order to direct future treatment strategies. We investigated the expression and activation of multiple growth factor receptors, their ligands and downstream signalling pathways in 30 meningiomas using immunohistochemistry. Expression was correlated with chromosome 22q loss. Membrane expression of VEGF receptor (VEGFR) and platelet-derived growth factor receptor (PDGFR)β was seen in 83% of tumors, Axl in 70%, EGFR in 50% and insulin-like growth factor receptor in 47%. Expression was similar in low- and high-grade tumors, but membrane EGFR expression was not seen in tumors showing chromosome 22q loss (P < 0.05). Expression of ligands (IGF, NRG, VEGF, Gas 6), and signalling proteins (Mek, Erk, Jnk, Akt) and pS6RP, was widespread. Western blot confirmed widespread Axl expression and supported selective expression of EGFR in NF2-intact meningiomas. The majority of meningiomas express and show activation of multiple growth factor receptors and their signalling pathways, irrespective of tumor grade. In addition to previously reported receptors, Axl offers a new therapeutic target. The findings also suggest that anti-EGFR based therapies may be less effective in meningiomas with 22q loss.

Genetic factors have been suggested to be involved in the pathogenesis of sporadic inclusion body myositis (sIBM). Sequestosome 1 (SQSTM1) and valosin-containing protein (VCP) are 2 key genes associated with several neurodegenerative disorders but have yet to be thoroughly investigated in sIBM. A candidate gene analysis was conducted using whole-exome sequencing data from 181 sIBM patients, and whole-transcriptome expression analysis was performed in patients with genetic variants of interest. We identified 6 rare missense variants in the SQSTM1 and VCP in 7 sIBM patients (4.0%). Two variants, the SQSTM1 p.G194R and the VCP p.R159C, were significantly overrepresented in this sIBM cohort compared with controls. Five of these variants had been previously reported in patients with degenerative diseases. The messenger RNA levels of major histocompatibility complex genes were upregulated, this elevation being more pronounced in SQSTM1 patient group. We report for the first time potentially pathogenic SQSTM1 variants and expand the spectrum of VCP variants in sIBM. These data suggest that defects in neurodegenerative pathways may confer genetic susceptibility to sIBM and reinforce the mechanistic overlap in these neurodegenerative disorders.

Encompassing all age-groups and locations, Pilomyxoid Astrocytomas constitute about 10% of all tumours previously diagnosed as Pilocytic Astrocytoma. Nearly two-thirds are hypothalamo-chiasmatic in location. Knowledge of this entity is essential for appropriate aggressive treatment and follow-up.

Loss of the Merlin tumour suppressor causes abnormal de-differentiation and proliferation of Schwann cells and formation of schwannoma tumours in patients with neurofibromatosis type 2. Within the mature peripheral nerve the normal development, differentiation and maintenance of myelinating and non-myelinating Schwann cells is regulated by a network of transcription factors that include SOX10, OCT6 (now known as POU3F1), NFATC4 and KROX20 (also known as Egr2). We have examined for the first time how their regulation of Schwann cell development is disrupted in primary human schwannoma cells. We find that induction of both KROX20 and OCT6 is impaired, whereas enforced expression of KROX20 drives both myelin gene expression and cell cycle arrest in Merlin-null cells. Importantly, we show that human schwannoma cells have reduced expression of SOX10 protein and messenger RNA. Analysis of mouse SOX10-null Schwann cells shows they display many of the characteristics of human schwannoma cells, including increased expression of platelet derived growth factor receptor beta (PDGFRB) messenger RNA and protein, enhanced proliferation, increased focal adhesions and schwannoma-like morphology. Correspondingly, reintroduction of SOX10 into human Merlin-null cells restores the ability of these cells to induce KROX20 and myelin protein zero (MPZ), localizes NFATC4 to the nucleus, reduces cell proliferation and suppresses PDGFRB expression. Thus, we propose that loss of the SOX10 protein, which is vital for normal Schwann cell development, is also key to the pathology of Merlin-null schwannoma tumours.